|Publication number||US6941036 B2|
|Application number||US 10/366,858|
|Publication date||Sep 6, 2005|
|Filing date||Feb 13, 2003|
|Priority date||Dec 21, 2000|
|Also published as||EP1356331A1, EP1356331A4, US6522800, US20020191889, US20040013342, WO2002052323A1|
|Publication number||10366858, 366858, US 6941036 B2, US 6941036B2, US-B2-6941036, US6941036 B2, US6941036B2|
|Inventors||Bernardo F. Lucero|
|Original Assignee||Bernardo F. Lucero|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (8), Referenced by (20), Classifications (34), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a Continuation-In-Part of application Ser. No. 09/745,977, filed Dec. 21, 2000, now U.S. Pat. No. 6,522,800, which has the same inventor as in the present application.
The present invention relates generally to micro-switches used in signal routing, and more particularly to relaying and routing signals in radio frequency (RF) switches and micro relays, power bus switches.
Signal processing is a very important part of modern technology. It is used in a wide variety of fields, such as in high-speed printing, image processing and telecommunications. Optical signals especially have become very important in recent years, since light travels at maximum speed and may not be vulnerable to interference problems that trouble electrical signals. As the definition of a composite signal increases by adding more pixels per inch, etc., it becomes necessary for signal processing equipment to handle larger and larger numbers of discrete signals in a smaller and smaller area. Equipment that switches the optical signals in these discrete channels must thus also be reduced further and further in size, a trend which has lead to the development of arrays of micro-switches.
These micro-switches can be made in a number of ways. A first type of switch uses electro-optically active material which can change its index of refraction or polarity when an electric field is applied. This type of switch can be effective, but may require the use of expensive materials, and generally require relatively high activation voltages.
Micro-machined devices of silicon (MEMS) is another approach to the fabrication of micro-switches. As the name implies, a wafer of silicon is machined by any number of processes including micro-sawing, etching, etc. to create a switching element which is free to move in some direction, either linearly or rotationally so that a signal can be directed from a first signal path into a second signal path as required. An actuator device is generally needed to move the switching element, and a problem has existed in getting each of these switching elements in an array which may include hundreds or thousands to go to precisely the same position when activated, and to return to the same position when deactivated. Since the spatial location of each incoming and outgoing beam must be precisely defined, if the switching element is not also precise in its positioning in both the activated and deactivated states, signal information may be distorted or lost.
Prior art switches include cantilever shafts which allow a switch element to be raised and lowered in and out of a beam path. These are less versatile and reliable than would be desired. It would be preferred to use switches in which the switching elements are free-standing, that is, completely unattached to the surrounding matrix material, however, these are difficult to produce and precise orientation of each of a great number of microscopic elements can be difficult to achieve.
Accordingly, there is a need for a micro-switch which can be made individually very small, and for which large multiples can be manufactured in large arrays. There is also a need for micro-switches which require only small activation voltages, are reliable, cost effective, and assume very precise positions both when activated and deactivated.
In addition, signal processing is a very important part of modern technology. It is used in a wide variety of fields, such as communications, data transmission, and testing. Switches of this nature can neatly fill the gap that exists between conventional silicon transistors and electromagnetic “macro-mechanical” reed relays and compete with electrostatic actuated micro-relays. Silicon transistors have the drawback of having finite “off resistance” and fairly large “open resistance” as compared to electromagnetic reed relays. Reed relays, on the other hand, typically dissipate a good deal of current (generating heat). Electrostatic relays do not carry the large currents of reed relay switches and does not have a strong applied force at the point of contact. Since reliability is of the utmost import in the relay business, and reliability is directly related to contact force, there are disadvantages to these kinds of switches.
Micro-machined devices made of silicon (MEMS) offer another approach to the fabrication of micro-switches. As the name implies, a wafer of silicon is machined by any number of processes including micro-sawing, etching, etc. to create a switching element which is free to move in some direction, either linearly or rotationally so that a contact can be made. An actuator device is generally needed to move the switching element, and a problem has existed in getting each of these switching elements in an array which may include hundreds or thousand to go to precisely the same position when activated, and to return to the same position when deactivated.
Thus, there is a need for a micro-switch which can be made individually very small, and for which large multiples can be manufactured in large arrays. There is also need for micro-switches that emphasize full switch functionality and manufacturability and provide strong contact force.
Accordingly, it is an object of the present invention to provide micro-switches which can be made very small.
Another object of the invention is to provide micro-switches which can be grouped in very large arrays.
And another object of the invention is to provide micro-switches which require only small activation voltages.
A further object of the invention is to provide micro-switches which can be very precisely positioned when in either the activated or deactivated state.
An additional object of the present invention is to provide a method of manufacture which employs the use of membranes, either primary or secondary or both, to aid in positioning the switching element or retain its position during fabrication operations.
Briefly, one preferred embodiment of the present invention is a microstructure switch having a main body, a moveable relay switching element, a first electrical contact positioned on the moveable relay switching element and a second electrical contact positioned on the main body. One or more membranes connect the moveable switching element to the main body and an actuator which moves the moveable switching element from a first position to a second position. The first and second electrical contacts are positioned such that when the actuator moves the moveable relay switching element from the first position to the second position, the first electrical contact makes electrical connection with the second electrical contact to complete an electrical circuit. The membranes may be either or both of a primary membrane or a secondary membrane. A primary membrane may be used as a temporary membrane which serves to position the moveable switching element until it is permanently positioned by a secondary membrane, or by an actuator. At this point the temporary membrane is removed.
Also disclosed is a method of manufacturing the micro relay switches.
An advantage of the present invention is that it is very cost effective to manufacture.
Another advantage of the invention is switching elements can be made completely free-standing, but the use of a membrane as a temporary positioning device makes fabrication operations much easier.
And another advantage of the invention is low activation voltages can be used, thus allowing cheaper and less expensive power supplies to be used.
A yet further advantage of the present invention is that an actuator mechanism can be included in a secondary membrane to make an integrated mechanism.
An additional advantage is the integration of components and elements other than switch elements onto the platform through subassembly.
These and other objects and advantages of the present invention will become clear to those skilled in the art in view of the description of the best presently known mode of carrying out the invention and the industrial applicability of the preferred embodiment as described herein and as illustrated in the several figures of the drawings.
The purposes and advantages of the present invention will be apparent from the following detailed description in conjunction with the appended drawings in which:
A first preferred embodiment of the present invention is a microstructure switch, which includes a multidirectional movable shaft that is made from and functions as an integrated component of a silicon micro-machined device, commonly known as MEMS. As illustrated in the various drawings herein, and particularly in the view of
The first embodiment of the microstructure switch 10, which is capable of multidirectional movement, is illustrated in its most basic form in
The switch 10 includes a wafer substrate 12, having a main body portion 13 and top surface 14, which has been etched to provide a top surface groove 16, as best seen in FIG. 2. This top-surface groove 16 surrounds shaft 18, which includes a platform 20, upon which various optical and signal path direction devices may be positioned or formed. The bottom surface 22 of the wafer 12 is then etched to form a bottom-surface groove 24. This preferably does not cut completely through to connect with the top-surface groove 16, but stops while a thin membrane, which will be termed the primary membrane 26, remains. The primary membrane 26 is created for the purpose of holding the shaft 18 in a precise position during the fabrication of the device, for maintaining position during the attachment of the actuator 30, and for ease of attaching or fabricating a device on to the platform 20.
The bottom-surface groove 24 surrounds a second shaft portion, which will be referred to as the shank 28. The shank 28 maintains attachment with the shaft 18, and may, as shown in the figure be of smaller diameter than the shaft 18, or may be continuous in diameter or even larger, as will be obvious to one skilled in the art. Similarly, the bottom-surface cutaway 24 is shown here to be of larger diameter than the top-surface groove 16, but this should not be construed as a limitation, as the relative diameters of the grooves 16, 24 may also vary. The entire moveable portion of the switch 10, including the shaft 18, shank 28, platform 20 and any optical elements or directing components (discussed below) which are formed from the shaft material, or added to the platform 20, will be referred to collectively as a moveable switching element 17.
As a variation, a second embodiment 50 is presented in
In this embodiment 50, there is a secondary membrane 52, which includes an actuator 30. Attachment has been made to the bottom side of the wafer 22 and then the primary membrane 26 is released from the shaft 18 and main body 13 using a chemical or mechanical process. The secondary membrane 52 has two primary functions, 1) precise and repeatable placement of the shaft 18 and platform 20 through the various ranges of movement and 2) to integrate an electrostatic, electromagnetic or other type of actuator 30 thus making a monolithic device. Also, the secondary membrane 52 may be pre-processed or pre-fabricated with patterns or devices prior to the attachment to the main structure 13. The advantages are having a device that operates with greater relative precision and repeatability and which is able to easily integrate other types of MEMS actuation methods.
It should be understood that although the primary and secondary membranes 26, 52 are shown as being continuous on all sides of the shaft 18, this is not necessary, and in fact either membrane 26, 52 could take the form of one or more tabs which join to the shaft 18 or shank 28 on only one or more sides, and not around the entire perimeter of the shaft 18 or shank 28.
In the mask 60, open areas 64 allow the passage of etching chemicals or reactive ion bombardment in the conventional manner of wafer etching.
Thus the primary membrane 26, and shaft 18 are made at the same time by etching a trench around the shaft 18 location, first from one side stopping at the etch stop layer 66 and then complete the membrane 26 by etching from the second side to the etch stop 66. As referred to above, the barrier is formed by either doping silicon or by thin film deposition or by time etch or using SOI (silicon-on-insulator) wafer as the start material. Placement of the membrane 26 can be on or near the surface of the silicon wafer 12, either on top or on bottom or located deep within the silicon close to or at the center of the wafer.
When the actuator has been attached to the shank 28, it can now serve to maintain the moveable switching element 17 in proper position and orientation, so the primary membrane 26 can now be broken or removed as seen in
In the case illustrated, the actuator 30 serves to move the moveable switching element 17 vertically, rather than acting to rotate it. Thus,
As mentioned above, the temporary primary membrane 32 may be removed once the device is fabricated and fully assembled. The method of removal is either by chemical or mechanically process to achieve complete separation of the shaft from the membrane and core material. The result is a shaft 18 that is independent (free standing) of the main structure 13 and is capable of moving in many directions.
Optionally, the membrane 26 is kept intact and is an integral component to the overall device 10. It functions to hold the shaft 18 in a precise position and it also serves to return the shaft 18 back to its original position. This design does limit movement to an arc or vertical direction and displacement is controlled by the pattern and size of the membrane 26. Varying the area, the thickness, the shape and/or pattern (perforation of various geometric design) of the membrane 26 affects its range of displacement and amount of flex force necessary for the actuator 30 to provide.
The actuation attachment point 70 is that area where the bonding to an actuator takes place. There are various methods for the attachment of the actuator 30 to the shank 28 and main structure 13, for example, the use of adhesive, soldering and other mechanical means. The actuator 30 could be in an array pattern or individual components that are aligned to the bottom side of the wafers or device and attached to the main body 13 and shank 28. Another approach is to attach a thin substrate like silicon, metal, glass or plastic material to the bottom side 22 of wafer 12 and fabricate an actuator 30 directly onto the secondary membrane 52. The type and design of the actuator 30 will determine the range of motion, speed and the directions that the device will be positioned. Generally, a displacement range of 100 μm is anticipated. Types of actuators include piezoelectric, electromagnetic, hydraulic, electrostatic and others.
The range of displacement of the shaft 18 is controlled by the actuator 30 or secondary membrane 52. It is possible to combine two or more directional movements in a single unit, for example, vertical movement with rotation.
The platform 20 will house any structure or directing component 76 that alters the signal, for example: mirrors, prisms, lens, electrodes and contact points, as well as, other passive devices and active devices (lasers or detectors). Although some components such as collimators, polarizers, gratings, filters, resonators and diffractive optical elements actually alter the character of the signal, rather than actually directing it, however, for the purpose of this application, the term “directing component 76” will be used to include these components as well.
Devices such as mirrors and prisms can be fabricated out of the wafer material 12 using surface and bulk micro-machining techniques. Other devices such as lasers, detectors and lenses can be mechanically attached to the platform. To achieve integration and build scalable planar structures, wafers can be pre-fabricated with devices and structures such as waveguides, V-grooves, optical platforms, electrodes, light source and detectors, active and passive components etc. The shape and size of the platform 20 is determined by the application of the device being fabricated or attached onto the platform 20. Optical applications where a device has been pre-fabricated can be modified using planar processing to make a moving shaft with a planar device on the platform. For example, a waveguide can be modified with a moving mirror or prism that is capable of altering the direction of the signal.
The microstructure switches 10, 50 can be used in a number of applications. Due to their small size, they are expected to be used in arrays having a large number of individual switches 10, all of which have been fabricated from a common wafer 12. They are expected to be incorporated into larger optical systems 100, of which many variations are shown in the following
One key use of the present invention is for the fiber optic industry. Such an implementation of an optical system 100 is shown in
An important feature of this design is the operating space of less than 50 μm between the input and output light channels. In both embodiments 10, 50, it is preferred that there is minimal free space on the top of the wafer 12 between the main body 13 and the shaft 18. Minimal space permits the switching element 10, 50 to be close to the source 84 and the outputs 86, 88 thus permitting the overall device to be small in size. In the communication arena, this concept reduces signal loss when the direction is altered or a connection is made. The idea of fabricating a shaft 18 from the base material 12 has many benefits like accurate, repeatable positioning of the shaft 18 in relationship to a source 84 and outputs 86, 88. Another advantage is having sufficient mass for maintaining a rigid and stable structure through the entire range of motion, as well as, holding its shape and supporting any structure attached or fabricated on to the platform 20. It will also dampen vibrations during the movement and while stopping or at rest. The result is a device with a fast settling time. By fabricating the shaft 18 from the wafer material 12 and locking it into position until final assembly, this ensures a stable, reliable and repeatable process of moving the shaft 18 from its original (home) position 72 to one or more activated locations 74 and back again.
It is to be understood that the present invention is not limited to having only a first output channel 86 and a second output channel 88. In the current example, it may be possible to have multiple output channels into which the mirror 90 directs the signal by its angular position. It should also be understood that the home position 72 and activated position 74 could be reversed so that, for instance, the mirror 90 could be located out of the beam path in home position 72 making the second output channel 88 active. The activator 30 may then push the mirror 90 upwards into the beam path 92 to make the first output channel 86 active when the switch 50 is in activated position 74. The activator 30 could also act to push or pull the directing component 76 from side to side rather than up and down, or could rotate the directing component, etc. The preceding examples are not to be construed as limitations, and many other variations are possible that would be obvious to one skilled in the art.
Listed below are other directing components 76 and optical systems 100 that can be implemented in conjunction with the switches 10, 50.
As referred to above, some components such as collimators, polarizers, gratings, filters, resonators and diffractive optical elements actually alter the character of the signal, rather than actually directing it, however, for the purpose of this application, the term “directing component 76” has been used to include these components as well. It will be obvious to one skilled in the art that many other components not listed here may also be included, either as off-the-shelf additions which can be placed on the platforms, or fabricated as integral parts of the switch.
Although the emphasis in the previous discussion has been on the variety of individual components which are usable as switching elements, it should be understood that these micro-switches will find their most common application in arrays of switches, in which multiple devices are included on a single wafer through a common fabrication process.
A second input beam 92 is shown entering lower input channeling device 83 and is passed by inactive devices 72 to reach active device 74, where it is reflected into output channel 89. it should be noted that the first and second input beams 92 cross at inactive device 75 without interfering with each other. Thus it is contemplated that multiple signals 92 may be channeled and switched within a single array 200 without interference.
It will be obvious to one skilled in the art that many variations in arrays and channel logic are possible. The number of channels is of course not limited to six, but many include hundreds or even thousands of directing components which are configured into arrays. It is preferred that the arrays include both rows and columns of directing components included in the array, so that, for instance, the beam directed into output channel 2 in
Although the main discussion above has been in regard to optical elements, another embodiment of the microswitches of the present invention uses them as electrical relay switches 300, of which one key use is for the testing industry.
One preferred features of this design is the matching angle of the contact surfaces (54.7 preferred) of the first contact 302 and second contact 304 to each other and the over lap of the contact. These allow for large and consistence surface contact, a scrubbing effect of the surface that will remove debris, and due to the direction of actuation a strong contact force being applied.
The preferred method of fabricating the micro relay switches is shown in
It will be understood that there are many other variations in the structure and fabrication of the micro relay switches. A few obvious variations are that there may only be first and second contacts, so that the relay acts as a single-pole-single-throw switch rather than acting as a bridge between second and third contacts. Also, the movable switching element may have the first contact material added later rather than being formed as an integral unit on the wafer. An example would be to fit a conducting cap piece onto the top surface of platform, in a similar manner to which optical elements are placed onto the platform as discussed earlier. The cap may form a sort of “T” shape with the shaft and may be activated by being drawn downward to contact the second and third contacts to complete the circuit.
Also it will be obvious that the relay switches can be configured so that the home position is when the circuit is opened and the activated position closes the circuit. These and other variations will be obvious to one skilled in the art.
As before, the micro relay switches can be formed in arrays which can be used to route signals through various paths.
While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
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|U.S. Classification||385/22, 385/15, 385/16, 385/13, 385/25, 385/18|
|International Classification||G02B6/122, G02B6/28, G02B6/35, G02B6/26, G02B6/12, G02B6/34|
|Cooperative Classification||G02B6/12004, G02B6/3546, G02B6/266, G02B6/3526, G02B2006/12159, G02B2006/12176, G02B6/3514, G02B6/122, G02B6/355, G02B6/2746, G02B6/2817, G02B6/3594, G02B6/3528, G02B6/3534, G02B6/352, G02B6/3584, G02B6/12007, G02B2006/12104|
|European Classification||G02B6/12M, G02B6/122, G02B6/12D, G02B6/35P10|
|Feb 27, 2009||FPAY||Fee payment|
Year of fee payment: 4
|Jan 23, 2013||FPAY||Fee payment|
Year of fee payment: 8